The proper practice of karate requires very extensive practice to perfect the various modes of attack; and some modes are very difficult to learn because they require body action of a character which is used for no other purpose.
Many karate students find that the karate kick is the most difficult maneuver to learn. The kick must be delivered by swinging the attacking leg up to one side of the body and striking with the side of the foot. An effective karate kick is delivered practically without bending the knee of the attacking leg; so it is particularly awkward move for most people to learn to do right.
Heretofore the usual training technique has required that the instructor hold a student's foot in his hand while the kick is learned and practiced; although, of course, after two students have learned the essentials of a proper kick they can work together. It is very difficult for a karate student to practice kicking technique alone.